1. Field of the Invention
The present invention relates to a cathode-ray tube display unit which can be manufactured with a reduced weight and with a flattened screen, such a display unit capable of being used In TV receivers and computer terminals, and a method of making such a display unit.
2. Description of the Related Art
FIGS. 1A, 1B, 1C and 1D illustrate a method of making a cathode-ray tube display unit. In these figures, reference numeral 2 denotes a complete panel which includes a panel glass, a fluorescent screen formed on the panel glass at the inner wall thereof and a color selecting mechanism suspended from the panel, such as a shadow mask. Reference numeral 3 designates a funnel which may be produced by applying graphite to the inner wall of the funnel glass. The complete panel 2 comprises a front display tube screen portion 2A and a side display tube panel portion 2B. The funnel 3 comprises a neck portion 4 extending backwardly from the back thereof, a frit seal portion 5 sealingly connecting between the complete panel 2 and the funnel 3, and an electron gun 8 sealingly mounted in the neck portion 4. Reference numeral 1 denotes a complete display tube body which includes the complete panel 2, the funnel 3 and the neck portion 4.
On manufacturing, the complete panel and funnel 2, 3 are first prepared, as shown in FIG. 1A. The complete panel and funnel 2, 3 are then sealingly connected to each other through the frit seal portion 5 which is made of frit glass, as shown in FIG. 1B. The complete electron gun 8 is sealingly mounted in the hollow end of the neck portion 4. The resulting display tube body 1 is then extracted through a tip tube 10 to form a cathode-ray tube display unit which is a vacuum glass enclosure, as shown in FIG. 1C. Since the interior of the display tube body 1 is a vacuum, the side display tube panel portion 2B of the complete panel 2 will be distorted in a direction of broken-line arrow X while the front display tube screen portion 2A will be distorted in a direction of broken-line arrow W. Under such a condition, the display tube body 1 is subjected to the activation of electrons and various tests. Since it is dangerous to leave the display tube body 1 as it is, however, the side display tube panel portion 2B of the complete panel 2 in the display tube body 1 is tightened by a metal band 9 to prevent an implosion, as shown in FIG. 1D. This completes the display tube body 1. At this time, as seen from FIG. 1D, the metal band 9 distorts the side display tube panel portion 2B of the complete panel 2 in a direction of solid-line arrow Z and also the front display tube screen portion 2A in a direction of solid-line arrow Y. The direction of solid-line arrow Z is opposite to the direction of broken-line arrow X while the direction of solid-line arrow Y is opposite to the direction of broken-line arrow W. Therefore, the distortion of the display tube body 1 due to the vacuum can be corrected by tightening the metal band 9.
FIGS. 2A and 2B illustrate a reduction of stress in the partial cross-section of the cathode-ray tube display unit which is manufactured through the process as shown in FIGS. 1A, 1B, 1C and 1D. A solid line in FIG. 2A shows the outline of the complete panel and funnel 2, 3 before the interior of the display tube body 1 is extracted. A broken line shows the outline of the complete panel and funnel 2, 3 after the interior of the display tube body 1 has been extracted. As will be apparent from FIG. 2A, the side display tube panel portion 2B bulges outwardly with the front display tube screen portion 2A being recessed inwardly, when the interior of the display tube body 1 is in vacuum. Thus, the metal band 9 is tightened about the side of the display tube body 1 to deform it into the position shown by the solid line. FIG. 2B shows the correction of distortion in another complete panel 2 which comprises a side metal portion 2C and a back metal portion 6. As will be apparent from FIG. 2B, such a complete panel 2 is also distorted as shown by a broken line when the interior of the display tube body 1 is extracted. However, such a distortion can be corrected by tightening the metal band 9 to deform the display tube body 1 as shown by a solid line.
In addition to the aforementioned process in which the complete panel and funnel 2, 3 are sealingly connected to each other with the electron gun 8 being sealingly mounted in the funnel 3 and the interior of the display tube body 1 is then extracted and subjected to the steps of preventing the implosion and distortion, there is also known another process of sealing between the complete panel 2 and the funnel 3, then treating the assembly for preventing the implosion and finally sealingly mounting the electron gun 8 in the display tube body. However, this also requires the metal band 9 for preventing the implosion.
The use of the metal band 9 about the side display tube panel portion 2B of the complete panel 2 increases the weight of the display tube body 1 and barely flattens the front display tube screen portion 2A. Since the cathode-ray tube display unit is entirely made of glass, it necessarily requires the metal band to strengthen the entire structure when the display tube body is extracted to form a vacuum. In order to correct the distortion and to prevent the implosion, the metal band is required even with a structure in which the glass body is partially strengthen by metal. Thus, the prior art could no further reduce the weight in the cathode-ray tube display unit and economically manufacture the cathode-ray tube display unit.